Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$222.69	11.766%	$248.8917	$248.89	$248.90	$248.90
Purchase #2	$114.37	9.210%	$124.9035	$124.90	$124.90	$124.90
Purchase #3	$112.26	13.427%	$127.3332	$127.33	$127.35	$127.30
Purchase #4	$134.90	7.198%	$144.6101	$144.61	$144.60	$144.60
Purchase #5	$6.53	13.773%	$7.4294	$7.43	$7.45	$7.40
Purchase #6	$131.88	8.743%	$143.4103	$143.41	$143.40	$143.40
Purchase #7	$167.92	10.597%	$185.7145	$185.71	$185.70	$185.70
7 purchase totals =	$890.55		$982.2927	$982.28	$982.30	$982.20